The present invention relates to a mold goods having a laminated flexible resin skin formed in a desirable location of the mold goods with an appreciable size, and an insert molding method suitable for manufacture of the mold goods.
As a conventional mold goods in which a skin lined with a foamed layer is attached on a base member such as a resin panel, a typical one is manufactured by a method in which a skin layer to be located at an outermost side of the product is premolded by a slash molding as well as a spray skin method or a vacuum molding method, and after this is inserted together with the base member, a polyurethane resin is injected and foamed as for a cushion layer between the skin layer and the base member.
As another well-known method, there is one that has begun to be employed, in which a sheet composed of a vinyl chloride or thermoplastic elastomer sheet (such as of an olefin system or urethane system, sometimes referred to as “TPO” or “TPU”, respectively) is lined in advance with a foaming layer made of a polyethylene foam (sometimes referred to as “PEF”) to provide a laminate sheet, which is absorbed for formation in a preheated female form, thereby being premolded in correspondence to the base member, and is attached by an adhesive or the like or inserted into an injection mold, to be insert-molded integrally with the base member.
For the protection of a cushion layer to have a secured durability against surface wear or such of products, the skin layer is unavoidable to interior parts of automobile that are required to stand the use in by far severe circumstances.
It also is important to provide an attachment strength between skin layer and cushion layer, and in the case of mold goods having application to the interior parts of automobile to be usually touched by hand or gripped for operation, the attachment strength (adhesion strength) between those layers, as well as their attachment strength to the base member, should be sufficient in level.
Japanese Patent Application Publication No. 2002-527263 has disclosed and example of conventional manufacturing method. In this document, disclosed technique needs two steps of molding process for molding a laminate of foamed layer and skin layer, and is troublesome, inefficient in productivity, and impractical.
Moreover, as a manufacturing method of a double-color mold goods by polyurethane resin material having an internal layer and thin skin layers, such a method is known that in a pressure-reduced form, a skin material is injected and attached on an inside of the form, and then a material for the internal layer is injected (for example, refer to Japanese Patent No. 3358416). This however needs a dedicated facility for pressure reduction of the cavity, and a mold to be high of air-tightness, besides a required time for pressure reduction to a prescribed pressure, and is very troublesome and costs high, so that one would have to say the employment is difficult.
Further, a combination of foamed layer and non-foamed skin layer of polyurethane is molded by a sequence of processes in a method, which also is known by Japanese Patent Application Laying-Open Publication No. 2004-58564 the covers and application by the present applicant. This method might be yet insufficient, as an increased uniformity is required between foamed layer and skin layer.
In particular, for such a large-scale mold goods as an upper facia of instrument panel, it is difficult to give an even tactile impression in a vicinity of an injection point (gate) and at a location distant therefrom, such that due to the non-foamed layer being thick at locations vicinal to the injection point and extremely thinned in thickness at location distant from the injection, the vicinity of the injection point has a firm touch while the location distant therefrom gives a very soft feel. The flow of polyurethane resin forming a skin layer may not arrive at locations further distant from the injection point, thus failing to have a skin layer spread over an entire product surface, with a resultant exposure of foamed layer in some cases, constituting a difficulty in applications to panel-like large-scale components or such.